<< Chapter < Page Chapter >> Page >
Graphs a, b, and c all plot number of cells versus time in days. In Graph (a), P. aurelia is grown alone. In graph (b), P. caudatum is grown alone. In graph (c), both species are grown together. When grown together, the two species both exhibit logistic growth and grow to a relatively high cell density. When the two species are grown together, P. aurelia shows logistic growth to nearly the same cell density as it exhibited when grown alone, but P. caudatum hardly grows at all, and eventually its population drops to zero.
Paramecium aurelia and Paramecium caudatum grow well individually, but when they compete for the same resources, the P. aurelia outcompetes the P. caudatum .

This exclusion may be avoided if a population evolves to make use of a different resource, a different area of the habitat, or feeds during a different time of day, called resource partitioning. The two organisms are then said to occupy different microniches. These organisms coexist by minimizing direct competition.

Symbiosis

Symbiotic relationships, or symbioses (plural), are close interactions between individuals of different species over an extended period of time which impact the abundance and distribution of the associating populations. Most scientists accept this definition, but some restrict the term to only those species that are mutualistic, where both individuals benefit from the interaction. In this discussion, the broader definition will be used.

Commensalism

A commensal relationship occurs when one species benefits from the close, prolonged interaction, while the other neither benefits nor is harmed. Birds nesting in trees provide an example of a commensal relationship ( [link] ). The tree is not harmed by the presence of the nest among its branches. The nests are light and produce little strain on the structural integrity of the branch, and most of the leaves, which the tree uses to get energy by photosynthesis, are above the nest so they are unaffected. The bird, on the other hand, benefits greatly. If the bird had to nest in the open, its eggs and young would be vulnerable to predators. Another example of a commensal relationship is the clown fish and the sea anemone. The sea anemone is not harmed by the fish, and the fish benefits with protection from predators who would be stung upon nearing the sea anemone.

Photo shows a yellow bird building a nest in a tree.
The southern masked-weaver bird is starting to make a nest in a tree in Zambezi Valley, Zambia. This is an example of a commensal relationship, in which one species (the bird) benefits, while the other (the tree) neither benefits nor is harmed. (credit: “Hanay”/Wikimedia Commons)

Mutualism

A second type of symbiotic relationship is called mutualism    , where two species benefit from their interaction. Some scientists believe that these are the only true examples of symbiosis. For example, termites have a mutualistic relationship with protozoa that live in the insect’s gut ( [link] a ). The termite benefits from the ability of bacterial symbionts within the protozoa to digest cellulose. The termite itself cannot do this, and without the protozoa, it would not be able to obtain energy from its food (cellulose from the wood it chews and eats). The protozoa and the bacterial symbionts benefit by having a protective environment and a constant supply of food from the wood chewing actions of the termite. Lichens have a mutualistic relationship between fungus and photosynthetic algae or bacteria ( [link] b ). As these symbionts grow together, the glucose produced by the algae provides nourishment for both organisms, whereas the physical structure of the lichen protects the algae from the elements and makes certain nutrients in the atmosphere more available to the algae.

Questions & Answers

What is abiotic
Mawen Reply
what is prokaryotit
Akanpanam Reply
Deoxyribonucleic Acid
Ernestina Reply
Gd evening guys pls some should help me with the excretory function of the kidney
Fonki
what is the full meaning of DNA
Taribo Reply
What is life
Abdulbaset Reply
what are oil immersion lenses
Theophilus Reply
no idea
Favour
what is cell targidity
Mi Reply
how will you determine the percentage of organic matter
Yussif Reply
the science of biotechnology has contributed to field of....?
David Reply
osagie
Osato
The class reptilia is a subdivision of the kingdom animalia and they are vertebrates, they consist of organisms which are oviparous, they possess homodont dentition, and do not show parental care, they also possess dry scaly skin.
Joseph Reply
what is class reptilia
SHARIFAH Reply
what is a enzymes
JAY Reply
what is a active site
JAY
what is a substrate
JAY
what is a product
JAY
A products is something that is made
Humphrey
Ok,what is a product?
Humphrey
an enzyme is an organic compound protein in nature that speed up the rate of reaction in the body of an organism
Ronald
why do we study biology
Babangida
what is the biggest part of a human brain
Kondwani
The biggest part of human body is the skin
John
I think it's celebrum
Ronald
hi ,how are you? Do you go Offline sometime or do you have other plans for Offline?We love this, but sometime to go on line is difficult.
Georgia Reply
hmmm , i don't really have much data , that why i went off line
Joy
what is anabolic
Chitu Reply
what is catabolic
jitu
What is classification?
GIFT Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?

Ask